The Pierce Run Dam, constructed by the Ohio Department of Natural Resources (ODNR), creates a water storage basin that helps treat the adjacent Pierce Run Stream for acid mine drainage. Water was not accumulating in the basin on a long-term basis. It was suspected that this was due to an underlying permeable unconsolidated layer that was allowing groundwater to flow under the dam.
B&N teamed with King Environmental Group, Bowser Morner, and Testing, Engineers & Consultants, Inc. to evaluate improvement plans and specifications prepared by ODNR and design and implement a solution.
B&N completed a hydrogeological investigation of the subsurface soils directly upgradient of the dam and produced a geologic cross section that delineated the suspect permeable unconsolidated layer. The team also identified potential issues with the original design and suggested alternative approaches to increase surface water and groundwater retention.
The team’s recommendations that were incorporated into the final design included:
- Grouting voids within the existing concrete block spillway to prevent water from infiltrating the dam’s internal structure
- Placing a bentonite/soil mixture across the dam’s upstream slope to reduce through-seepage
- Grouting two existing, damaged 48-inch HDPE overflow pipes and inlets that were originally installed through the center of the dam and replacing them with one 36-inch catch basin and 18-inch overflow pipe near the top of the dam to minimize flow across the spillway at peak times
- Keying the bentonite/soil slurry wall into the surrounding bedrock walls to prevent seepage
Two weeks after the improvements were completed the upstream storage basin was full. The basin continues to retain the water used for long-term treatment of acid mine drainage.